Electron-discharge device



April 21, 1925.

E. F. w. ALEXANDERSON ELECTRON DISCHARGE DEVI'CE Original Filed Sept.28, 1920 rm/enter Ernst F'. W Alexander-son,

y JQW 4% His Attor-he y.

' Patented Apr. 21, 1925.

. UNITED STATES ERNST r. w. ALEXANDERSON, or SCHENECTADY, NEW YORK,

COMPANY,

ELECTRIC ASSIGNOR T GENERAL OF NEW YORK, N. Y.

ELECTRON-DISCHARGE DEVICE.

Application filed September 28, 1920, Serial No. 413,337. Renewed March12, 1923.

To all whom it may concern:

Be it known that I, ERNST F. W. ALEX- ANDERSON, a citizen of the UnitedStates, residing at Schenectady, county of Schenectady, State of NewYork, have invented certain new and useful Improvements inElectron-Discharge Devices, of which the following is a specification.

The present invention comprises a novel electron discharge device whichis particularly adapted to the controlling and amplifying of electricalcurrents.

Heretofore electron discharge devices have been constructed in which thetransmitted current was subject to the control of a variable magneticfield. In these devices the cathode was axially arranged with in theanode, preferably being substantially equidistant from the anode at allpoints along its length.

I have discovered that an even more sensitive device can be constructedby locating the anode centrally with respect to the oathode, andpreferably spacing the electrodes symmetrically.

I have illustrated diagrammatically in Fig. 1 a form of apparatusembodying my invention; Fig. 2 is a diagram illustrating an electricalcharacteristic of my device, and Figs. 3 3* and 3 illustrate visuallyelectron flow under various conditions as an aid to explain myinvention.

The device shown in Fig. 1 is adapted for use as an amplifier for weakelectrical currents, for example, radio signals. It comprises anelongated glass envelope 1 containing a centrall located elongated orrodlike anode 17 an a helical cathode 2 symmetrically surrounding theanode. The cathode 2 is preferably although not neces 'sarilyequidistant from the anode 17 atall points, along its length and ingeneral I prefer to arrange the electrodes in devices embodying myinvention in circular symmetry with respect-to each other.

The cathode 2 is adapted to emit electrons independently of the passageof current across the space between the electrodes; for example, in thecase illustrated in the figure the cathode consists of refractorymaterial, preferably tungsten, connected by conductors 3, 4, to asuitable source of electric energy represented by an electric battery 5.A regulable resistance 6 is provided to control the heating current. The

anode 17 may also consist of tungsten and various other metals may alsobe used. The space within the envelope is evacuated and the parts of thedevice are deprived of gas to such an extent that the electron discharge can occur therein without material gas ionization. A slightamount of gas ionization will do no harm,-but it should not be so highas to make the electrons uncontrollable by a magnetic field. Somesuitable means for generating a variable magnetic field is provided, as,for example, a coil 7 which has been diagrammatically shown adjacent tothe discharge tube, but which, as in devices of this type, willordinarily surround the tube. This coil 7 is connected to the source ofweak variable current which is to be amplified, as repre sented in thiscase by the conductors 8, 9.

There is also provided some means for generating a. polarizing electricfield, as represented by coils 10 and 11, connected in series to a.source of direct current such as a battery 12 in circuit with a variableresistance 13. In circuit with the electrodes 2 and 17 are included asuitable source of direct current as represented by the battery 14 and asuitable indicating device such as a telephone receiver 15.

When no exterior magnetic field is applied to an electron dischargedevice having an anode centrally located with respect to the cathode theelectrons in general tend to move in direct paths from the cathode tothe anode, as shown in Fi 3". When a magnetic field is generatedsubstatntially parallel to the cathode, the electrons are deflected outof a direct path. With a central location of the cathode in priordevices the path of the electrons tend to become curved as shown in Fig.3. When the magnetic field is increased sufliciently the electronseventually travel in a long spiral path about the cathode on their wayto the anode and finally when the field strength is increasedsuficiently electrons will fail to reach the anode by reason of thisdeflection.

In a device having a centrally located anode the electrons flowinginwardly from the surrounding cathode to the anode when deflected by amagnetic field as shown in Fig. 3 are caused to travel in a generaldirection tangentially to the anode and tend to form orblts about theanode. As the centrifugal force of the mass of electrons .magnetic fieldmust be strong enough to overcome the centrifugal force of the electronsin their circular path. The relation between the magnetic field tending"to defiect the electrons and the current transmitted by the device isindicated by the dia-' gram constituting Fig. 2, the values of themagnetic field being plotted as abscissae and the corresponding fieldvalues as ordinates for a given cathode temperature. As the strength ofthe magnetic field is increased from zero the current remainssubstantially constant until the magnetic field reaches a valuerepresented as oo on the abscissae. further increase of field strengthcauses a rapid reduction of current until at a field strength of 0?)current has fallen substantially to zero.

The magnetic field necessary to produce a decrease in current, in otherwords, the value 0a will be less in a device embodying my invention thanin devices heretofore constructed having a centrally located cathode. Inpractice the strength of the polarizing magnetic field is adjusted atsome value between 0a and 0?). Consequently when the variable magneticfield of the coil 7 is superimposed upon the polarizing field anincrease or decrease of conductivity of the device occurs. For examplewhen the variable magnetic field produced by the coil 7 tends to assistthe polarizing field generated by the coils 10 and 11, the current inthe circuit 16 tends to decrease, and conversely, when the magneticfield of the coil opposes the polarizing field the current in thecircuit 16 increases. Therefore, a variable current in the circuit 8, 9produces a corresponding amplified variable current in the circuit 16which can be used in any desired manner, as in a telephone receiver 15.

What I claim as new and desire to secure by Letters Patent of the UnitedStates, is,- 1. In combination, an electron discharge device adapted tooperate independently of gas ionization comprising the combination of ananode, an electron-emitting cathode arranged about said anode andmagnetic means arranged to oppose the passage of electrons from saidcathode to said anode.

2. In combination, an electron discharge device comprising an evacuatedenvelope, an electron-emitting cathode and an anode inclosed by saidcathode and having a major axis extending in the direction of the majoraxis of said cathode and means for producing a magnetic field parallelto the axis of symmetry ofsaid electrodes for controlling the flow ofelectrons from said cathode to said anode.

-3: An electron discharge device comprising the combination ofelectrodes contained in an evacuated space, the cathode comprising acoiled conductor, the anode being located substantially centrally withinsaid coiled conductor, and means for generating a magnetic fieldsubstantially parallel to the axis of said cathode.

4. An electron discharge device comprising the combination of anelongated anode, a helical cathode symmetrically spaced about saidanode, means for heating said cathode, an enclosing evacuated envelopeand magnetic means for controlling an electrical discharge between saidelectrodes.

5. An electron discharge apparatus comprising the combination of anelongated electrode, a helical electrode spaced about the same, meansfor conducting an electric current through said helix, a sealedevacuated envelope enclosing said electrodes, a load circuit connectedto said electrodes, and a magnetic winding located to generate amagnetic field substantially parallel to the axis of said helix.

6. An electron discharge device com rising in combination an evacuatedenve ope, an elongated anode, a filamentary cathode symmetrically spacedabout said anode, and means for generating a magnetic fieldsubstantially parallel to the axis of said cathode.

7. An electron discharge device comprising in combination an evacuatedenvelope, an elongated anode, a helically coiled cathode symmetricallyarranged about said anode, means for heating said cathode to atemperature sufiiciently high to emit electrons, magnetic means forproducing a field which will deflect electrons out of a direct pathbetween said electrodes, means for varying said field, and a loadcircuit connected to said electrodes.

8. An electron discharge apparatus comprising the combination of ananode, an electron-emitting cathode arranged about said anode, anenclosing evacuated envelope, an output circuit connected thereto,magnetic means for generating a field opposing the passage of electronsfrom said cathode to said anode and input means for varying said field.

In witness whereof, I have hereunto set my hand this 27th day ofSeptember, 1920.

ERNST F. W. ALEXANDERSON.

